Automatic switching arrangement for electric motors



C. A. M WEBER.

AUTOMATIC SWITCHING ARRANGEMENT FOR ELECTRIC MOTORS.

APPLICATION.F|LED JULYJI, ms.

1,316,009. PatentedSept. 16,1919.

//y. WITNESSES: INVENTOR JlffiordA. M-Weben A'rroRNEY so-called split-phase CLIFFORD A. M. WEBER,

INC-HOUSE ELECTRIC PENNSYLVANIA.

OF EDG-EWOOD PARK, YENNSYIIVAK IA, ASSIGNOR TO WEST- AND MANUFACTURING COMPANY, A COBIOBA'IION OF AUTOMATIC SWITCHING ABBANGEMENT FOR ELECTRIC MOTORS.

Specification of Letters Patent. Patented Sept, 16, 1919.

Application and Jul 11, 1916. Serial No. 108,575.

To all whom it may concern:

Be it known that I, CLIFFORD A. M. WVEBER, a citizen of the United States, and a resident of Edgewood Park, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Automatic Switching Arrangements for Electric Motors, of which the following is a specification.

My invention relates to automatic switching systems for reversing electric'motors and is particularly adapted for use in connection with motors that are provided with auxiliary starting devices and are dependent in operation upon motor-speed conditions.

Motors of the. above-described type include single phase commutator motors that. are adapted for repulsion operation during the starting period and for induction operation after reaching a predetermined speed, and other single-phase motors of the type that are provided with auxiliary starting windings which are operative only during the starting period. It is well known that a single-phase induction motor will not reverse when current is reversed in itsgwindings unless the reversing switch is held open long enough to allow the starting wmding, or other automatic starting device, to become effective. Since the operation of the starting winding or other device is usually dependent upon the speed of the motor, it is obvious that it requires considerable judgment'on' of the operator in order to throw thereversin switch over at the proper moment. It is a so obvious that the-apparatus driven by the motor may be damaged, or its operation seriously interfered with when the motor fails to reverse because of improper manipulation of the reversing switch. Or, it may be desirable to provide for the reversal of a direct-current motor only when the motor is operating below a predetermined spec n n It is the object of my invention to provide a" switching, arrangement for reversing an electric motor by means of which it is impossible for current to be reversed in the motor 'prior to the operation of a suitable speed-controlled device, regardless of direcwith a commutator cylinder device 7 is also mounted the part tion in which the reversing switch may be thrown.

In the accompanying is a diagrammatic view of my switching system as applied to a single-phase motor of the repulsion-induction type, and Fig. 2- is a view, similar to Fig. 1, showing my invention as applied to a motor of the splitphase type.

The motor shown in Fig. 1 comprises a field magnet land-an armature 2 provided 3 having shortcircuited brushes 4 cooperating therewith. A centrifugally-actuated short-circuiting device 5 is mounted on the shaft 6 of the armature 2 and is adapted to short-circuit the segments of the commutator cylinder when the motor reaches a, predetermined speed. The short-circuiting device 5 may be one of several well known types, such, for example, as the device shown in Patent No. 1,090,328. A centrifugally-actuarted circuit-controlling on the shaft 6 and may be of any known t pe but is referably constructed in aocor ance with t disclosure in a copending application, Serial No. 863,569, filed Se '0. 24, 1914, by G. W. Hansell and assigne to the Westinghouse Electric & Manufacturing Company. The device 7 generally comprises a composite ring 8 that is adapted to expand or contract in accordance wit the speed of the shaft 6. A reciprocally-mounted me her 9, that is longitudinally stationary with respect to the shaft 6, is provided with projections 10 and 11 that are adapted to be engaged by the inner and outer peripheries of the ring 8, respectively, the ring being shown in its contracted form and the member 9 in its lower position.

In Fig. 1, the exciting winding is diagrammatically shown at 12, and the revers-. in or auxiliary winding at 13. One terminal of the main winding .12is connected to the left-hand stationary contact member 15 of an electrically-operated switch 151 and drawings, Figure 1 the other terminal thereof is connected to.

the left-hand, movable contact member 16 of a three-pole double-throw reversing switch 17. The respective terminals of the upper left-hand and center stationary conreversing winding 13 are connected to the tact members 18 of the switch 17. The lower left-hand and center stationary contact members 19 of the switch 17 are permanently cross-connected to the corresponding upper stationary contact members 18, as is customary in reversing switches. The middle movable contact member 16 is connected to the left-hand stationa contact member 20 of the switch 14. T e righthand contact members 15 and 20 of the switch 14 are respectively connected to the mains 21 of a suitable single-phase source of energy through the double-pole singlethrow switch 22. The plunger 23 of the switch 14 is provided with bridging members 15" and 20 which are normally disengaged from the corres nding contact members when the actuatlng coil 24 is deenergized. One'terminal of the actuating coil 24 is connected to one side of the line and the other terminal thereof 'is connected to the upper right-hand stationary contact member 18 through the stationary contact terminals 25 and bridging member 25 of the circuit-controlling devlce 7; The bridging member 25 is mounted on the reciproeating member 9 and is in engagement with the contact members 25 when the composite ring 8- is in its contracted form. The lower right-hand contact member 19 is permanently connected to the corresponding contact member '18 of the switch 17, and the right-hand movable contact member 16 is connected to the other side of the line. The olding or maintaining contact members 27 of the switch 14 are connected in shunt around the contact members 25. A bridging member 27 is carried by the lunger 23 and is out of engagement with t e contact members 27 when the coil 24 is deenergized.

Having described the various parts comprising my switching arrangement, the operation is as follows: When the switch 22 is closed and theswitch 17 is in its neutral position, the coil 24 is not energized and the bridging members 15, 20, and 27, respectively, are disengaged from their corresponding contact members. The motor being at rest, the composite ring 8 is in its retracted form and the bridging member 25 is in engagement with the contact members 25. When the switch 17 is closed in the upper position, the coil 24 is energized through the contact members 25, thereby drawing the core 23 upwardly and bridging the respective pairs of contact members 15, 20 and 27. The main field winding 12 and the reversing winding 13 are thereby connected in series-circuit relation across the mains 21, and the motor starts as a repulsion motor. When the motor reaches a predetermined speed, the operation of the device 5 causes the commutator-cylinder to be short-circuited, and the motor operates as an induction motor. At a second preside of the brush 4 left-hand contact determined speed, the composile ring 8 expands sufficiently to withdraw the bridging member 25' out of en agement with the contact member 25. e current in coil 24 then flows through the holdin or maintaining contact members 27. The above-described conditions prevail as long as the switch remains closed in its upper position.

When it is desired to reverse the motor, the switch 17 is thrown to its lower position while the motor is operating at full speed. As the blades of the switch 17 leave the upper stationar contact members 18, the circuit ofthe 0011 24 is interrupted and the switch 14 opens, thus disconnecting the motor from the mains 21. The motor then decelerates and, when the predetermined speed is reached, the short-circuiting device 5 is withdrawn fromv the commutator cylinder 3. A further decrease in the s eed of the motor causes a contraction of t e ring 8 which moves the bridging member 25' downwardly into engagement with the contact members 25. The circuit of the solenoid 24 is then reestablished, and the switch 14 closes, thus permitting'current to again traverse the windings 12 and 13. As the current in the windlng 13 is now reversed, the total resultant field is shifted from one to the other, producing the same effect as if, without reversing the current in the winding 13, the brushes were shifted from one side of the neutral axis to the other, as in the ordinary repulsion motor. As the motor is now adapted for repulsion operation the motor continues to decelerate to a standstill and then accelerates in the opposite direction. a

It is obvious that the arrangement described with reference to Fig. 1 may be as readily applied to a direct-current motor with only the omission of the shortcircuiting device 5.

The core member 1 of the motorv shown in Fig. 2 is provided with a main windin 28 and a startin winding 29, the axes of w ich are displacef 90 electrical degrees with respect to each other. The armature 30 of the motor is provided with a squirrel-cage windin 31, and a centrifu ally actuated device 7, similar to the one described with reference to Fig. 1, is mounted on the armature shaft 32. The terminals of the main winding 28 are connected to the upper lefthand and middle contact members 18 of the switch 17 and the corresponding movable contact" members 16 are connected to the members 15 and 20 of the electrically operated switch 14. The connections of t e actuating coil 24 are the same as described with reference to Fig. 1. The terminals of the starting winding 29 are connected to the line between the switches 14 and 17, one terminal being connected through the contact members 33sand an additional bridging member 33" that is mounted on the reciprocating member 9 of the device 7.

Having described the various parts with respect to Fig. 2, the operation of the motor is as follows: When the switch 17 is closed in its upper position, current from the mains 21 traverses both the main and starting windings 28 and 29, and the motor starts as a split-phase motor. At a predetermined speed, the expansion of the ring 8 draws the bridging members 25 and 33 out of engagement with the corresponding contact members, thereby interrupting the circuit of the starting winding 29 and causing the current in the coil 24' to flow through the holding or maintaining contact members 27 and bridging .member 27. When the switch is thrown to its lower position, circuit of the coil 24 is interrupted and the switch 14 opens. It is then impossible for the current to reverse in the winding 28 until the contraction of the ring 8 restablishes the circuits of both the starting winding29 and the actuating coil'2 1.

It is apparent from the above that my switching arrangement automatically disconnects the motor from the current source until the speed-responsive devices have operated and'that the reversing switch may be thrown to any position, while the motor is operating at ful speed, without interfering with the operation thereof or damaging the windings of the motor itself.

While I have shown my invention as specifically applied to induction motors of the repulsion-induction and split-phase types, it is not so limited but may be as readily applied to other types of induction motors and to direct-current motors. I desire, therethe' fore, that only such limitations shall be imposed as fall within the scope of the appended claims.

I claim as my invention:

1. The combination with a source of electrical energy, an electric motor provided with a main winding and a centrifugallyactuated starting device, and a reversing switch for connecting said motor winding to said source, of means responsive to the operation of said centrifugally-actuated device for preventing a reversal of current in the winding of said motor until said starting device becomes efltective.

2. The combinationwith a source of electrical energy, an electric motor provided with a main winding and a centrifugallyactuated starting device, and a reversing switch for connecting said motor winding to said source, of a switching device the operation of which is dependent upon said centrifugally-actuated device for preventing a reversal of current in the winding of said motor until said starting device becomes effective.

3. The combination with a source of electrical energy, an electric motor provided actuated starting device, and a reversing switch for connecting said motor winding to said source, of an electrically-operated switching device connected between said reversing switch and said source, the control circuit of which is operatively connected with said centrifugally-actuated device and said reversing switch.

In testimony whereof, I have hereunto subscribed my name this 29th day of June,

CLIFFORD A. M. WEBER.

wlth a main winding and a centrifugally- 

